How to simulate glass dispersion with only one Principled BSDF node
Interesting question. I think it'd be near impossible to do this as accurately as mixing glass nodes, but if absolute realism isn't your aim then of course your options open up.
Using a procedural texture at very small scale I was able to get this effect in cycles:

Although this is definitely not an accurate way of doing it, it does appear to be somewhat realistic and quite beautiful provided you have some good lighting. (Psst... HDRI)
The values in the colour ramp I did using the HSV mode and just changing the H value.
The Hex values are: Black: #000000, Red: #FF0000, Green: #01FF00, Blue: #0001FF, and Black: #000000.
Let me know if there is something missing and I'll edit this response to include it.
Hope this helps!